An “atomizer” is a dispenser that turns a liquid into a fine spray. For some applications, atomizers are used to spray a fuel or other liquid into a hot environment.
In the case of fuel atomizers, the fuel can undergo chemical changes leading to carbonaceous dry materials that plug the atomizer if the fuel temperature is not maintained below the thermal oxidation temperature, typically in the range of 200° C. to 300° C. This chemical degradation of the fuel due to thermal oxidation is often referred to as fuel “coking.”
Similarly, in spraying urea-water mixtures into the exhaust of engines as part of a selective catalytic reduction (SCR) system for control of nitric oxide (NO) emissions, the atomizer can sometimes overheat and cause the water to vaporize, leaving behind solid urea particles that plug the atomizer.
In the design of fuel atomizers or other atomizers, the liquid flowing through the atomizer is also used to cool the atomizer and to avoid chemical changes in the liquid that can lead to atomizer plugging. However, in some applications, such as fuel injection atomizers, the atomization is intermittent. The atomizer remains in place in the hot environment when no liquid is flowing through the atomizer. Overheating of the liquid in the atomizer under these conditions can cause atomizer plugging and failure.
A solution to this problem can be achieved if the atomizer temperature can be maintained below the temperature at which the liquid undergoes thermal degradation. To cool the atomizer and avoid thermal decomposition, water or engine coolant is often used. However, routing cooling water to the atomizer is often difficult, expensive, or impractical.